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https://issues.apache.org/jira/browse/HDFS-1796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13070976#comment-13070976
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Bharath Mundlapudi commented on HDFS-1796:
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Fair lock guarantees the order of execution at the cost of performance. If
delete and read arrives at the same time but read operation takes the lock
first, without fair lock, system might schedule delete operation first and then
read. Shouldn't we care about the correctness and order of execution in file
systems?
> Switch NameNode to use non-fair locks
> -------------------------------------
>
> Key: HDFS-1796
> URL: https://issues.apache.org/jira/browse/HDFS-1796
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Hairong Kuang
> Attachments: non-fair-lock.patch
>
>
> According to JavaDoc, a non-fair lock will normally have higher throughput
> than a fair lock. Our experiment also shows an improved performance when
> using a non-fair lock. We should switch namenode to use non-fair locks.
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